Eventually k-Bounded Wait-Free Distributed Daemons

Proceedings of the Twenty-First Annual Symposium on Parallelism in Algorithms and Architectures

Welch

2009

Self Cite

Dining philosophers is a classic scheduling problem for local mutual exclusion on arbitrary conflict graphs. We establish necessary conditions to solve wait-free dining under eventual weak exclusion in message-passing systems with crash faults. Wait-free dining ensures that every correct hungry process eventually eats. Eventual weak exclusion permits finitely many scheduling mistakes, but eventually no live neighbors eat simultaneously; this exclusion criterion models scenarios where scheduling mistakes are recoverable or only affect performance. Previous work showed that the eventually perfect failure detector (3P) is sufficient to solve wait-free dining under eventual weak exclusion; we prove that 3P is also necessary, and thus 3P is the weakest oracle to solve this problem. Our reduction also establishes that any such dining solution can be made eventually fair. Finally, the reduction itself may be of more general interest; when applied to wait-free perpetual weak exclusion, our reduction produces an alternative proof that the more powerful trusting oracle (T ) is necessary (but not sufficient) to solve the problem of Fault-Tolerant Mutual Exclusion (FTME).

Section: Introductionmentioning

confidence: 89%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The weakest failure detector for wait-free dining under eventual weak exclusion

Proceedings of the Twenty-First Annual Symposium on Parallelism in Algorithms and Architectures

Welch

2009

Self Cite

“…This safety property models systems where resources are recoverable or where sharing violations precipitate only transient (repairable) faults. Applications of 3WX include shared-memory contention management [6], conflict managers for self-stabilizing systems [7], and wait-free eventually fair daemons [8].…”

Section: Contributionsmentioning

confidence: 99%

“…For example, 3WX models recoverable resources where sharing violations precipitate at worst repairable (transient) faults. 3WX has received considerable attention recently in the context of shared-memory contention management [6], conflict managers for selfstabilizing systems [7], as well as wait-free eventually fair distributed daemons [8].…”

Section: Introductionmentioning

confidence: 99%

Wait-Free Dining Under Eventual Weak Exclusion

Song

Distributed Computing and Networking

Self Cite

Abstract. We present a wait-free solution to the generalized dining philosophers problem under eventual weak exclusion in environments subject to crash faults. Wait-free dining guarantees that every correct hungry process eventually eats, regardless of process crashes. Eventual weak exclusion (3WX ) actually allows scheduling mistakes, whereby mutual exclusion may be violated finitely-many times; for each run, however, there must exist a convergence point after which live neighbors never eat simultaneously. Wait-free dining under 3WX is particularly useful for synchronization tasks where eventual safety is sufficient for correctness (e.g., duty-cycle scheduling, self-stabilizing daemons, and contention managers). Unfortunately, wait-free dining is unsolvable in asynchronous systems. As such, we characterize sufficient conditions for solvability under partial synchrony by presenting a wait-free dining algorithm for 3WX using a local refinement of the eventually perfect failure detector 3P1.

Eventually Perfect Failure Detectors Using ADD Channels

Parallel and Distributed Processing and Applications

2007

Self Cite

Abstract. We present a novel implementation of the eventually perfect failure detector (3P) from the original hierarchy of Chandra-Toueg oracles. Previous implementations of 3P have assumed models of partial synchrony where point-to-point message delay is bounded and/or communication is reliable. We show how to implement this important oracle under even weaker assumptions using Average Delayed/Dropped (ADD) channels. Briefly, all messages sent on an ADD channel are privileged or non-privileged. All non-privileged messages can be arbitrarily delayed or even dropped. For each run, however, there exists an unknown window size w, and two unknown upper-bounds d and r, where d bounds the average delay of the last w privileged messages, and r bounds the ratio of non-privileged messages to privileged messages per window.